The field of the invention relates to computer tomography and more particularly to x-ray medical computer tomography.
Computer tomography (CT) using cone-beam projection technology typically employs an x-ray source to form a vertex in the shape of a cone. A scanning orbit of the x-ray source is a curve along which the vertex of the cone beam moves during a scan. A set of detectors are disposed at a fixed distance from the cone-beam source. Methods currently exist which have established a relationship between cone-beam projections and a first derivative of the three dimensional (3D) Radon transforms of such projections. Theoretically, each source position "S" can deliver Radon data positioned on a sphere, the Radon shell of "S." The corresponding spheres on a circular orbit sweep out the Radon space of the object, referred to as a torus. Regions inside the smallest sphere containing the object, but exterior to the torus, is called the shadow zone. The shadow zone characterize the region where Radon data is missing from the circular orbit.
When using a circle-and-line orbit, the line-orbit data is typically used for filling in the shadow zone. Even though the shadow zone is very small, as compared to the volume of the entire valid Radon data delivered by the circular orbit, current cone-beam projection techniques are computationally intensive. Accordingly, a need exists for simplifying image reconstruction based on the circle-and-line orbit.